Apparatus for controlling or checking the irregularity of a flow of textile or like materials



g- 1960 A. BUTI'ICAZ ETAL 2,950,436

APPARATUS FOR CONTRQLLING OR CHECKING THE IRREGULARITY OF AFLOW OFTEXTILE OR LIKE MATERIALS Filed April 15, 1957 I 4 Sheets-Sheet 1 f7 I 8I YV/IVVEIYTOKS I 9. 46f flrvoe 5077/662 CH/QBLES 72-34 45 f/z-v/vzEMBOWJK/ f 454 C 8y JAW' if Aug. 23, 1960 A. BUTTICAZ ETAL 2, 5 ,4 6

APPARATUS FOR CONTROLLING OR CHECKING THE IRREGULARITY OF A mow OFTEXTILE OR LIKE MATERIALS 4 Sheets-Sheet 2 Filed April 15, 1957 Aug. 23,1960 A. BUTTICAZ ET AL APPARATUS FOR CONTROLLING OR CHECKING THEIRREGULARITY OF A FLOW OF TEXTILE OR LIKE MATERIALS Filed April 15, 19574 Sheets-Sheet s Aug. 23, 1960 A. BUTTICAZ ETAL 2,950,436

APPARATUS FOR CONTROLLING OR CHECKING THE IRREGULARITY OF A FLOW OFTEXTILE OR LIKE MATERIALS Filed April 15, 1957 4 Sheets-Sheet 4 UnitedStates Patent APPARATUS FOR CONTROLLING OR CHECKING THE IRREGULARITY OFA FLOW OF TEXTILE OR LIKE MATERIALS Andr Butticaz, 45 Rue de la Bolle,Charles Tesage, 24

Rue Folmard, and Heinz Dembowski, 92 Rue de la The present inventionrelates to a method and apparatus for controlling or checking theirregularity of a flow of textile or like materials, with a view tomeasuring and/or recording the irregularities of strips, ribbons, wicks,threads, etc., made of textile material or other like materials.

The invention has also for its object to provide an indication andcounting of the difference, either above or below, exceeding apre-determined percentage with respect to a given mean value. I

An indication of this kind ofiers in particular the possibility ofdetermining the frequency of an irregularity observed in a How ofproducts resulting from a process of manufacture and to permit of theidentification, for example, by means of measurement of the period or ofthe wave-length of the irregularity of the member or the stage of themanufacture which may be the cause.

The invention constitutes an application and a development of the methoddescribed in the U.S.A. patent specification filed October 1, 1956,under No. 613,099, for Process and Apparatus for Controlling a Flow ofTextile Fibres or Similar Materials, and consisting essentially incausing the flow of material to be controlled between the two plates ofa condenser and in measuring the increase in capacity of this condenserwith respect to its value in the absence of the material: under certainconditions which are always obtained in practice, this variation incapacity is proportional to the mass'of textile or like materialintroduced between the plates of the measuring condenser. Mention hasbeen made in the above-mentioned patent of the advantageous use of adifferential condenser forming a measuring condenser and a referencecondenser on each side of a central plate, in association with meansknown per se as a whole, to translate the variationsin capacity of themeasuring condenser into a control signal. It is this same arrangementwhich has again been adopted in the scope of the present invention witha view to the formation of a regularimeter capable of checking theirregularity of a flow (thread, wick, strip, ribbon, etc.) of textilematerial or the like.

The method in accordance with the invention consists essentially incausing the flow of material to be controlled to pass at a constant butadjustable speed through a measuring condenser, in producing an electricout-ofbalance signal resulting from the comparison of the capacity ofthis measuring condenser with the capacity of a reference condenser, incomparing this out-of-balance signal with a signal which represents amean reference value, and in controlling the variations of thedifferential signal resulting from this comparison and representing theirregularity.

In accordance with one method of procedure, a mean fixed pre-determinedreference value is adopted corresponding to the nominal characteristicsof the flow of material under control, and in this case any irregularitywill be termed an absolute irregularity.

In accordance with a further method of procedure, a variable meanreference value is adopted corresponding to the mean real value of thesignal obtained during a limited period of time preceding the instant ofobservation, and in this case the irregularity will be termed a relativeirregularity.

Whether it is a question of absolute or relative irregularity, itsinstantaneous value may be observed and/or recorded in magnitude and insign by means of appropriate instruments.

With a view to the determination of a mean value of the irregularity, afull-wave rectification is effected of the differential signal obtainedby a comparison of the actual value of the signal with the mean value ofreference, this rectification being followed by an integration oflimited memory of the differential signal thus rectified. The result ofthis integration may be indicated in an intermittent manner at the endof each of a succession of discrete periods of integration, or again itmay be indicated and/or recorded in a permanent manner.

These controls will preferably be completed by a detection with a viewto counting and indicating the crossing, by the actual value of thedifferential signal representing the irregularity, of two pre-determinedthreshold values which are respectively positive and negative, thefrequency of these crossings supplying information as to the frequencyof the irregularity. Before being subjected to this detection ofdeparture outside a range of values, the signal will preferably befiltered in a low pass filter with an adjustable cut-off frequency,which enables the elimination at will of variations in frequency greaterthan a certain value for a given speed of fiow.

The apparatus proposed for the purpose of carrying the method describedinto effect comprises in accordance with a preferred form of embodiment,a measuring cir cuit formed by a high frequency oscillation generatorwith a symmetrical output, a differential condenser comprising at leastone measuring condenser and one reference condenser formed by twoexternal plates arranged symmetrically on each side of a central plate,the outer plates being comiected to the terminal of the said generator,a tuned amplifier, means for applying to the input of this amplifier theout-of-balance potential of the said central plate, a detector connectedto the output of the amplifier, and an interpretation apparatuscomprising a continuous reference source of potential and means forcontrolling variations of the differential signal resulting from thecomparison of the potential delivered by the said detector with thereference potential.

For the purpose of varying its gain, the amplifier will preferably beprovided on the one hand with a manual regulating device and on theother hand with an automatic control device operating with apre-determined time-constant, either the one or the other of thesedevices being put into use, depending on whether it is desired toobserve the absolute or relative irregularity.

The interpretation device will preferably comprise a differentialaperiodic amplifier with two input terminals which are respectivelyconnected to the reference source and to the detector; the differentialsignal delivered by this amplifier will be passed in the first place toan indicating and/or recording instrument by means of which variationsin irregularity can be observed, and in the second place to arectifier-integrator intended to determine the mean value of theirregularity, and thirdly to a device for detecting, indicating andcounting the passages of the irregularity beyond two threshold values,respectively positive and negative, and which are separately adjustable.

The special features and advantages of the invention will become furtherapparent from the description which follows below of a form ofembodiment given by way of example, reference being made to theaccompanying drawings in which:

Fig. 1 is a general diagram of the apparatus.

Fig. 2 is an explanatory diagram of the operations of measurement ofirregularity.

Fig. 3 is a diagram relating to the operation of selec tion and countingof amplitude.

Fig. 4 is a perspective view of the measuring con denser.

Figs. 5, 6 and 7 are front views of the three first plates of thiscondenser.

Fig. 8 is a view in cross-section taken along the line VIIIVIII of Fig.7.

Fig. 9 is a diagram showing the measuring circuit and the gain-controldevice of the amplifier.

Fig, 10 is a detail view in cross-section of a part of the amplifiercasing.

Fig. 11 is a diagram showing the shape of the fre quency-response curveof the automatic gain-control device.

Fig. 12 and Fig. 12a taken together are an electrical diagram of theinterpretation apparatus unit.

In accordance with the form of embodiment shown diagrammatically in Fig.l, and intended to control the irregularity of a strip, ribbon, wick orthread 10, the latter is caused to pass at a constant speed, by means ofa pair of driving rollers 11, coupled to a motor (not shown), betweenthe central plate 12- and one of the outer plates 13, 14 of an aircondenser of the symmetrical or differential type. Each of the armatures12, 13 and 14 is framed in known manner by corresponding keeperofantistr-ay plates 12', 13 and 14' held at the potential of the mountingframe and intended to make the electric field uniform between the platesby eliminating the edge effects. The outer plates 13, 14 are connectedby symmetrical wires 15, 16 to the two terminals of a balanced outputtransformer 17 of an oscillator 18, the centre point 19 of the secondarywinding of this transformer being connected to the earth of theassembly. 4

The central plate 12 is coupled through a coupling condenser 20 and aleakage resistance 21 to the input grid of a tuned amplifier 22. Theoutput signal from this amplifier is simultaneously applied to the inputof two detectors 23 and 24. The detector 23 supplies an automaticgain-control 25 for the tuned amplifier 22. This gain may also becontrolled by a manual regulation shown by the arrow 26. The detector 24supplies an interpretation device, of which the unit is indicated by thereference 27.

The interpretation device comprises a differential amplifier 28, to theinput of which is applied on the one hand the detected voltage from 24,and on the other hand a continuous reference potential or datumpotential supplied by a source of reference 29. The differential signalresulting from this comparison is applied in the first place to anindicator instrument 30 with a central zero, enabling an instantaneouspositive or negative value to be read at any moment.

The signal is applied in the second place to a rectifier integrator 31,to the output of which is connected an indicating instrument 32 withleft-hand zero, enabling the mean integrated value to be read with acertain timeconstant of the said differential signal. The latter isfinally applied in the third place to a device 33 known as an amplitudecounter and comprising two indicator lamps 34, 35 of different colours(red and green for example) and arranged so as to light the first lampwhen the signal passes over a pre-determined and adjustable positivethreshold value, and to light-up the second lamp when the signal passesover a negative threshold value which is also predetermined-andadjustable. p

Before beginning the detailed description of an example of constructionof these various elements of the apparatus in accordance with theinvention, and in particular of the interpretation device, withreference to Figs. 4 to 12, the method of measurement or control of theregularity will first of all be explained with reference to Figs. 2 and3,

If a great length of thread, wick or ribbon is weighed per unit oflength, centimetre by centimetre, for example, there is obtained a curvethe general shape of which is that shown by the curve in full linesgiven in Fig. 2, in which P is the weight per unit of length, plotted asordinates, and L is the length plotted as abscissae. By integrating acurve of this kind, or by dividing the total weight by the total length,a mean weight Pm can be determined; the straight line MM parallel to theaxis of the abscissae, at an ordinate value Pm, would be the curve of aperfectly uniform thread of the same metric number. The metric number Nmis the term given to the quotient of the length in metres by the weightin grams; it is thus the reciprocal of the mean weight as defined above.By irregularity is meant the deviation of the real curve from the idealstraight line MM: it is thus essentially a variable quantity, changingin sign at a certain frequency, depending on the conditions ofmanufacture of or treatment of the thread, Wick, ribbon, etc

In accordance with the invention, it is proposed on the one hand tomeasure the mean value of the irregularity, and on the other hand toobtain information as to the frequency of its variations.

The o-ut-of-balance signal applied to the input of the amplifier 22being proportional to the mass of textile or like material which islocated at any instant between the plates of a measuring channel, thesame thing will be true of the amplitude of the signal applied to theinput of the detectors 23 and 24 with the reservation that the potentialdelivered does not pass out of the range of linearity of the amplifier.The rectified voltage will, under these conditions, be subjected tovariations in function of time corresponding to the curve in full linesas shown in Fig. 2, the time scale being obviously coupled to the scaleof lengths L by the speed of passage adopted. By varying the gain of theamplifier in such manner that for a thread, strip or ribbon of meanweight Pm, the rectified voltage will be equal to the referencepotential of the source 2 (see Fig. 1), it is seen that the instrument3%) will indicate at every instant the instantaneous value of theirregularity as defined above, and this instrument may with advantage hegraduated directly in percentages, on each side of the central zero.

The control of the gain of the amplifier may be effected either by handor automatically. In the case of manual regulation, the gain iscontrolled in a fixed manner, using a previous calibration as a base, toa value such that the detected potential applied to the input of thedifferential amplifier 28 is equal to the reference potential of thesource 29 for a predetermined nominal weight or metric number. Themeasurements of the irregularity will then be carried outwith respect tothis predetermined nominal or theoretical weight, and it is this thatwill be termed an -absolute" measure of the irregularity.

In the case of automatic control of the gain by means of the circuit 25,the gain will be automatically controlled in such manner that therealmean level of the detected potential remains constantly adjusted to thereference potential, the said mean level being established with acertain time-constant proper to the circuit 25, that is to say on thebasis of an integration of the output potential with a limited memory.The measurements of the irregularity will then be effected with respectto this real mean weight measured over a certain length of thread,ribbon or strip, and it is this measurement which will be termed arelative measurement of the irregularity.

In the rectifier-integrator 31, the signal passing out of thedifferential amplifier 28 is first subjected to a fullwave rectificationwhich supplies a quantity corresponding in Fig. 2 to the curve formingthe upper contour of the shaded surface, this curve being obtained byreversing in symmetry with respect to the straight line MM, all thenegative half-waves of the irregularity curve. By integration of thisrectified signal, there is then obtained a mean level Em, and the ratioEm/Pm will represent the desired mean value of the irregularity, whichwill be preferably indicated directly as a percentage on the instrument32 which is graduated from zero to 100%. This value will be an absolutemean value in the case of a manual control of the gain, fixing thestraight reference line MM at a level corresponding to a predeterminedtheoretical nominal weight or metric number; it will be a relative meanvalue in the case of automatic gain control, in which case the straightreference line MM will in fact be replaced by a slowly-varying curvehaving ordinates which correspond at every instant to the real meanweight of a certain length of thread which has previously passed throughthe measuring condenser. v Finally, in order to obtain information onthe periodicity of the irregularity, there is arbitrarily fixed apositive threshold B, (see Fig. 3) and a negative threshold value E withrespect to the mean value MM and the periods of overrunning p p 11 n n nof these two respective threshold values will be observed. Thisoperation is efiected in the device 33 known as an amplitude counter,the positive over-runs p and .the negative over-runs n being indicatedrespectively by the lighting of the two lamps 34, 35. This device willpreferably comprise a low-pass filter with an adjustable cutofl!frequency which enables the variations, the frequency of which exceedsthe cut-off frequency to be eliminated for a given speed of passage andin consequence to smooth-down the curve examined to a correspondingextent.

Figs. 4 to 8 show a preferred form of embodiment of the measuringcondenser. With a view to a better adaptation of the threads, wicks andribbons, the condenser is provided with four measuring channels, ofwhich two are for the threads. To this end, it is provided with nineplates 41 to 49, each separately fixed by means of screws on a base 50.Both plates and base are of electrolytic copper; the surfaces arepolished and chromiumplated in order to prevent wear and corrosion, andto reflect thermal and light radiations.

As can be seen in Fig. 5 for example, with respect to the first plate41, an internal zone such as 41a of small surface has been cut-out ofeach plate, this zone being insulated from the external zone 41'!) by alayer 410 of insulating low-loss material such as mica or trolitul forexample. In each plate, the inner zone a forms a plate of the condenser,whilst the outer zone forms the corresponding keeper plate. The plate 42thus forms the central plate and the plates 41 and 43 are the two outerplates of a first differential condenser or first measuring channel. Theplate 44 of smaller height than the preceding plates forms the centralplate of a second differential condenser or measuring channel; it isenclosed between the plates 43 and 45. The central zone 43a of the plate43 thus forms an outer plate at the same time for the first and for thesecond measuring condenser; as shown in Figs. 7 and 8, it is cut-outwith a bevelled edge, so that its face turned towards the plate 42a ishigher than that turned towards the plate 44a, which is smaller than4201. The same condition applies for the inside zone of the plate 45which is associated at the same time with condensers No. 2 and No. 3,and for the inner zone of the plate 47 which forms part simultaneouslyof the condensers No. 3 and No. 4.

Figure 9 shows the diagram of the measuring and gain-control circuits.

Three parallel wires 51, 52, 53 are stretched to form a flat surface ina hollowed-out portion formed for that purpose in the base of themeasuring condenser (see also Fig. 10): the central plates 42a, 44a, 46aand 48a are connected to the central Wire 51, whilst the outer platesare respectively connected to the outer wires 52 and 53. Two screws 54and 55 can be passed at will either between the Wires 51, 52 or betweenthe wires 51 and 53; the first is used for the zero setting or thebalancing of the measuring condenser, whilst the other, when it is fullyscrewed home serves to produce a welldefined change in capacity for thepurpose of calibration of the apparatus. This calibrating screw isnormally unscrewed.

The oscillator comprising a tube 60 is of a standard type with a gridcoil 61, a plate coil 62 tuned by a condenser 63 and a balanced couplingcoil 64 having a centre point earthed. The working frequency is forexample 100 kilocycles per second. The oscillator assembly is placed ina compartment 65 of a screened casing 66, of which a further compartment67 contains theinput stage of the amplifier. The base 68 of themeasuring condenser carries two threaded rods 69, 70 which passrespectively into the compartments 65 and 67 inside insulating guidetubes 71 and 72 respectively. The rod 69 carries a magnetic core 73 onwhich is formed the coupling coil 64. The tube 71 carries the grid coil61 and plate coil 62 arranged round the coupling coil 64. The couplingcoil 64 comprises a bi-filar winding, and it is connected by plaitedconnection wires 73 to the outer wires 52 and 53 of the measuringcondenser.

The central wire 51 of the measuring condenser is connected by a wire 74to the coupling condenser 20, already referred to in connection withFig. 1. This condenser is formed by a cylindrical condenser comprisingan inner plate 75 carried on the threaded rod 70 by means of aninsulating core 76, and an outer plate 77 carried on the insulating tube72.

The base of the measuring condenser thus forms a single unit with itscoupling members to the oscillator on the one hand and the amplifier onthe other. The arrangement described ensures however a strict separationof the oscillator from the amplifier, avoiding all direct induction,both electro-magnetic and electro-static; it also avoids any verydelicate direct contacts in the coupling zone, since an even very smallchange in contact resistance would result in phasing errors and inconsequence in errors of measurement.

The construction of the amplifier 22 itself does not give rise to anyspecial difficulty and will not be described in a detailed manner;although a relatively high gain is desirable, it is possible to avoidthe necessity for frequency changing and to employ only a directamplification. It will be necessary to take precautions in respect ofthe construction of the first stage, which should be decoupled in aparticularly efiicient manner on the one hand with respect to highfrequency, and on the other hand to suppress all the residual hum of thehigh tension, which will be stabilised. At the output, a push-pull stagewill preferably be provided in order to feed the two detectors 23 and 24by means of a transformer 80 having two identically similar secondaries.

The cathode of the first amplifier tube 81 may be connected either to afixed resistance 82 or to a group of three potentiometers 83, 84 and 85.This changeover is effected by means of a change-over switch 1 with fourblades and three positions a, b and c. The position a corresponds to themanual gain-control, the position c to automatic control, whilst theposition b is an intermediate transition position. A resistance 86arranged in parallel with the tube 81 and its load 87, formed in theusual manner by a circuit tuned to the frequency to be 7 amplified,forms with the cathode resistance 82 or 83 to 85 a potential dividerwhich tends to compensate for the effect on the gain of the first stage,of any possible variations of the anode potential, by a correspondingvariation of the potential of the cathode.

It will be noted that in the manual gain control position (position a ofthe switch I), the control grid of the tube 81 is connected through theleakage resistance 21, the wire 88 and the wire 89 to the slider of thepotentiometer 85. In the automatic control position (position 'c), it isconnected by the wire 88 to the output of the filter with tworesistance'capacity sections 91--92 and 9394, the input of which is thenconnected by the wire 95 to the negative terminal of the detector 23,whilst the positive terminal of this detector is connected by a wire 96to the slider of a potentiometer 97 inserted in a series potentiometergroup 98 connected between the high tension supply and earth. The wire88 is connected on the other hand through a diode 99 to a point 90 ofthis group, which fixes a maximum limit (+4 volts for example) to thedirect current potential of the grid.

The slider of the potentiometer 97 being fixed on the other hand at ahigher potential which is known as the positive reference potential (of+65 volts for example), it can be seen that the potential applied to theinput of the filter is the result of the comparison of the detectedpotential with this reference potential.

In the position b of the switch I, the resistances 91 and 93 areshort-circuited and the filter is reduced to two condensers 9'2. and 94in parallel: the change-over to this position enables the condensers 92and 94 to be instantaneously charged and thus avoids useless waitingperiods. In the position 0, the filter is inserted between the inputwire 95 and the output wire 88. A damping resistance 100 arranged inseries with the first condenser 92 serves to attenuate the resonance bypositive reaction which tends to be produced at a certain value offrequency, by reason of the double de-phasing effect.

Fig. 11 shows the shape of the response curve obtained under theseconditions: the magnitudes plotted in abscissae are the frequencies ofthe variations of the amplitude of the input signal, that is to sayvariations in the capacity of the measuring condenser resulting fromvariations in the thickness of a thread, for example, whilst asordinates there have been plotted the relative values at which thesesame variations are found at the output side of the amplifier. It can beseen that the effect of very slow variations (low frequencies) iscompletely suppressed by the regulation; that there is then anintermediate zone in the vicinity of the opening frequency f of thefilter, a resonance zone r of slightly higher value, and a progressivetransition to the normal zone at which the variations of the outputsignal faithfully reproduce those of the input signal. By introducingthe notion of wave-length of the variations in irregularity of thethread or ribbon under study, that is to say the ratio of the speed ofpassage to the frequency of the variations, it can be said that theautomatic regulation causes the suppression of the effect in the outputsignal of the variations of long-waves lengths, that is to say ofwavelengths definitely greater than a wave-length of cutofi; it is clearthat this wave-length of cut-off is proportional,'for a given thread, tothe speed of passage and that, in consequence, by increasing this speed,it is possible to progressively cause to appear in the output signalvariations which are slower and slower and the effect of which waspreviously suppressed.

These considerations :show a further aspect of the difference betweenthe absolute measurement and the relative measurement of theirregularity: with the absolute measurement (manual gain regulation) allthe variations appear both slow and rapid; the relative measurement(automatic gain regulation) suppresses the variations having frequencieslower that the opening frequency f0 "of the filter forming theregulation circuit, or in other 8 words, the variations in wave-lengthgreater than the Wave length corresponding to cut-off. This Wave-lengthbeing however proportional to the speed of passage, an increase in thisspeed will have the effect of bringing closer together the relativemeasurement and the absolute measurement.

The description can now be given of one form of em bodiment of theinterpretation device itself, with reference to the diagram shown inFig. 12. The rectified potential delivered by the detector 24,represented by U is compared with a positive reference potention U0,taken froma potentiometer group 101 provided for that purpose betweenthe positive of the stabilised high tension supply and earth. A seriesof calibrated resistances 102 to 105, connected between the output ofthe detector and the tapping 106 on the potentiometer group, enables hewhole or a fixed fraction of the differential potential U-U0 to betaken-off by means of a rotary switch 107, and thus to obtain varioussensitivities of measurement. Thus, for example, in the first positionmarked 12.5%, the Whole of the said potential is taken-off through theintermediary of a series protecting resistance 108; in the position 25%,one-half; in the position 50%, onequarter, and in the position oneeighth of the said potential. The two last positions R and B are used inthe calibration operations of the apparatus.

The signal taken-oil by the switch 107 is transmitted by theintermediary of a low-pass resistance-capacity filter 109110, which canbe put partly or wholly out of action by means of a double change-overswitch II with three positions: in the position a, the filter is out ofaction (condenser open circuited, resistance short-circuited); in theposition b, the resistance remains short-circuited, but the condenser isin circuit and in practice absorbs the very rapid variation; in theposition 0 the entire filter is inserted and produces a damping of thefrequencies greater than its cut-off frequency; this facilitates asearch for the mean on long wave-lengths. I

The signal taken from the output of this filter passes through one ofthe four contacts of a four-pole switch with two positions (a, b) orreversing switch III in order to be brought by a wire 111 to the controlgrid of a differential amplifier 28 with two tubes 113, 114 connected asa cathode-follower circuit; the signal is collected at low impedancebetween the cathodes at 115 and 116, at the head of two load resistances117, 118 of equal values. The grid of the second tube or reference tube114 is connected to the slider of a potentiometer 119, connected inparallel to the bridge 101 on each side of the reference potentialtapping 106.

In position a of the reversing switch III, the indicator 30 with acentre Zero is connected between the points 115 and 116, and in theposition b of the said reversing switch; the indicator 32 with left-handzero or integration indicator is connected between the same points 115and 116 Suitable variable resistance 121, 122 are respectively connectedin series with these two instruments. In addition, there is permanentlyconnected between the output terminals 115 and 116 of the amplifier abranch containing a variable resistance 1'23 and a jack 124 intended topermit of the connection of a recorder by means of a plug. Theresistance 123 is short-circuited when the plug is engaged in the jackand replaces the recorder when the latter is disconnected, so as toavoid a modification of the total impedance coupled between theterminals .115 and 116.

The signal available between the terminals 115 and 116 of thedifferential amplifier is on the other hand simultaneously applied tothe input of the rectifier-integrator 31 and to a device known as theamplitude-counter, the whole of which is indicated by the reference 33.

The rectifier-integrator 31 comprises essentially a bridge of diodes 132 intended to charge an integrating condenser 134 (of'2 microfarads forexample) by the full-wave rectifled signal potential, through theintermediary of a load resistance 133 of very high value (20 megohms forexample). The load resistance is shunted by a push-button 135 whichenables the condenser 134 to be charged or discharged instantaneouslyduring a checking of the calibration. In parallel with the integrationcircuit 133-134 is connected an auxiliary source of voltage 136, of 20volts for example, in series with a resistance 137 of 2 megohms forexample. This auxiliary circuit is provided in order to make thedischarge resistance practically equal to the charge resistance, thisbeing an essential condition in order to obtain a correct integration,that is to say a good linearity and a very low threshold of excitation.The integration is effected with a memory limited to periods of theorder of the time-constant, or forty seconds with the values given byway of example. For long lengths of thread, a number of successiveintegrations will thus be carried out, separated by periods of aboutthirty seconds for example.

After each integration period, the reversing switch III is turned overto the position b, which has the effect of changing-over the positiveplate of the integrating condenser 134 to the slider of a potentiometer120 connected in parallel with the potentiometer 119, and its negativeplate to the grid of the tube 113: the instrument 32 is substituted atthe same time for the instrument 30, and its deflection indicates themean level of the irregularity during the period of integrationconsidered.

The amplitude-counting device 33 comprises at its input a variableloss-pass filter 140141 which has a cut-off frequency variable betweencertain limits, so that the variations of frequency greater than thiscut-off frequency will be eliminated from the signal passed to thecounter. The signal having passed through this filter is applied throughthe medium of a protection resistance 142 to the slider of apotentiometer 143 forming part of a potentiometer chain connected acrossthe terminals of an auxiliary polarising source 144, of about 20 voltsfor example. Two other potentiometers 145 and 146, forming a secondchain at the terminals of the source 144 have their sliders connected tothe grids of two thyratrons 147 and 148 through the intermediary of therespective coupling resistances 149 and 150. Condensers 151 and 152 areconnected on the other hand between the grid and the cathode of each ofthe thyratrons. The latter are supplied between cathode and anode by asource 153 of alternating-current potential and are loaded respectivelyby the relay windings 155 and 156, shunted in the usual manner by acondenser-resistance combination 157, 158.

The contacts of the relays 155 and 156 control, one at rest and theother in the Working position, the lighting of the respective lamps 34and 35, one of which is intended to indicate the passage above and theother the passage below two given threshold values. These two lamps aresupplied from an alternating source 159 of 6.3 volts for example. Therelays operate in addition the respective counters 161 and 162.

Finally, a switch 160 is arranged between the input of the device andearth: when this switch is closed, a highly negative potential isapplied to the grids of the thyratrons (the cathodes of which arebrought up to the potential of the output 116, or +60 volts forexample), so that the counting is then stopped.

As the thyratrons become active at a certain negative value of thebiasing potential of their respective grids, thjere results an asymmetrybetween the behaviour of the two thyratrons, which is compensated for bymeans of the potentiometer 143; in other Words, this potentiometerserves to ensure the symmetry of behaviour of the two thyratrons withrespect to a zero input voltage corresponding to the reference line MMof Fig. 3. The potentiometers 145, 146 serve on the other hand to fixrespectively the passage of the lower threshold E2, below which therelay 155 operates to light the lamp 35, and the passage of the upperthreshold E1, above which the relay 156 operates to light the lamp 34.

It is known that the operation of thyratrons supplied on the anode withalternating current and controlled at the grid by a continuous or slowlyvarying potential, is unstable in a circuit of the kind employed here:the firing curve is actually displaced, depending on the value of thedirect current potential at the terminals of the condenser which shuntsthe anode load, and this results in hunting. This drawback is avoided inthis case by means of the resistance-capacity sections 149151 and 150152, which play the part of stabilisers. By a suitable choice of thetime constant of these sections, an excellent regularity of operation isobtained, the difference between the firing and extinction thresholdsbeing reduced to about 0.5 volt for example, for an anode potential ofvolts R.M.S. The time-constant of the stabilising sections will be ofthe order of magnitude of the period of the alternating potential of theanode supply. The results indicated above were obtained, for example,with a supply at 50 cycles per see. with resistances 149, 150 of 10megohms and condensers 151, 152 of 2,000 micromicrofarads.

The form of embodiment which has just been described is simple andeconomical in construction and has the additional advantage of beingvery easy to use. In particular, it lends itself to a calibration andre-calibration which is both rational and simple, so that the operatorhimself can regularly carry out a check of the calibration and even acomplete re-calibration which may be made necessary from time to time bythe inevitable wear of the electronic tubes. In this way, returning theapparatus to the works and visits of technicians are avoided, both ofwhich are costly and useless, since the complete calibration can becarried out in a time of the order of one minute.

Calibration comprises the following operations:

After checking and when necessary correcting, in the usual mannerthe,zero settings of the indicating instruments and also the supplyvoltages, the rotary switch 107 (Fig. 12) is first of all placed in theposition B, and the change-over switches I, II and III in the positiona. The reference potential is then applied to the input of thedifferential amplifier 28. By acting on the potentiometer 119, theneedle of the indicator 30 is brought back to Zero. The push-button isthen depressed for half a second, to short-circuit the load resistance133 of the integrating condenser and ensure the discharge of the latter,the reversing switch III is then changedover to the position b; as theinstrument 32 should then indicate zero, its deflection is adjusted byacting on the potentiometer 120.

The rotary change-over switch 107 is then put into the position R(equivalent to the position 100%); in the absence of a signal, thecentre-zero instrument 30 should then indicate -100%. This deflection isadjusted by acting on the series resistance 122. By depressing theshort-circuited button 135, the instantaneous charge of the integratingcondenser 134 is ensured at the maximum potential corresponding to 100%irregularity: after having turned the reversing switch III into theposition b, the series resistance 121 is adjusted, if this is necessary,so as to bring the instrument 32 to the corresponding deflection, afterwhich the reversing switch III is brought back to the position a.

The manual gain control potentiometer 84 (see Fig. 9) is provided with aregulating dial graduated in usual values of metric number or of nominalweight of thread, strip, ribbon, etc., depending on the applicationsconsidered. This is placed on a reference mark corresponding to theminimum nominal weight or maximum metric number provided for. Thezero-setting screw or balancing screw 54 of the measuring condenser isthen regulated so as to bring the needle of the irrggurality indicator30 to the position l00%: this amounts to the same thing as adjusting thebalance of the measuring condenser in the absence of material undertest. The calibrating screw 55 is then introduced fully into the screwedhole provided for that purpose; the change in capacity produced by thiscalibrating screw replaces the change in capacity which would be causedby a standard of textile or like material, since it is not possible toestablish a durable standard of such material. The other potentiometer83 of the manual gain control device is then adjusted so as to bring theneedle of the indicator 30 into the position +100%.

Still keeping the calibrating screw fully engaged, the dialpotentiometer 84 is brought into another position marked for thatpurpose, and for which the third potentiometer 85 of the manualgain-control device is adjusted so as to bring the needle of theinstrument 30 onto a corresponding mark situated at 80% for example. Thecalibrating screw is then disengaged.

t only remains to adjust the reference potential employed in theautomatic gain-control circuit, in opposition to the potential detectedby the detector 23, that is to say the position of the slider of thepotentiometer 97 (see Fig. 9). For this purpose, there is introduced forexample a thread of average metric number into the measuring condenser,and the rotary change-over switch (Fig.

12) is put into the position of maximum sensitivity (12.5% for example);the potentiometer 97 is then adjusted so as to bring the needle of theindicator 30 opposite its central zero. It is thus made sure that theautomatic gain-control device really tends to regulate the potentialdelivered by the detector 24 to a value equal to the reference potentialU which is employed at the input of the interpretation device.

The calibration is then finished and the apparatus is ready for use. Itcan be seen that the various adjustments are entirely independent onefrom the other, that is to say they have no mutual influence on eachother. This particularly useful property enables, in addition, anarrangement to be employed such that the various regulating andadjusting members on the control panel of the apparatus are eachdisposed either opposite the reference mark as a function of which it isto serve, or is characterised by a colour matching with that of thismark; these two methods may of course also be combined. Thus, forexample, the spindles of the potentiometers 83 and 85 which will beoperated by a screwdriver will be placed opposite the two respectivereference marks of the scale of the potentiometer 84, on to which thislatter has to be brought during the corresponding adjustments; thespindles of the potentiometer 119 and of the rheostat 112 will be placedrespectively opposite the positions B and R of the rotary change-overswitch 107 opposite which the knob of this switch should be placedduring the corresponding adjustment, etc.

It will be appreciated that this arrangement still further facilitatesthe operation of calibration and enables all risk of error or confusionto be avoided.

The invention is of course not limited to the forms of enbodiment chosenand shown, these having been given by way of example only; the inventionmay, on the contrary be given various alternative forms which will beclearly apparent to those skilled in the art, both as concerns theconstruction of the condenser and the measuring circuit and also that ofthe interpretation device itself.

What We claim is:

1. In an apparatus for determining the irregularity of a continuous flowof textile or like materials, the combination comprising, a differentialcondenser having a central plate electrode, an external plate electrodesymmetrically disposed on each side of said central electrode, so as toform a measuring condenser and a reference condenser; means for passingsaid continuous flow between the central plate electrode and theexternal plate electrode forming said measuring condenser; an oscillatorhaving a central output terminal and two external output terminals whichare symmetrical with respect to said central terminal; a measuringcircuit, to determine the difference between the capacities of saidmeasuring and reference condensers, comprising said oscillator, saiddifferential condenser, an output impedance element, means forsymmetrically connecting one of said external terminals of saidoscillator to said external plate electrode forming said measuringcondenser and the other of said external terminals of said oscillator tosaid external plate electrode forming said reference condenser, andmeans for connecting said output impedance element to said central plateelectrode on the one hand and to said central output terminal of saidoscillator on the other hand; a tuned amplifier; means for connectingthe input of said amplifier across said impedance element; a detectorcoupled to the output of the said amplifier; an interpretation devicecomprising a source of continuous reference potential and meansconnected to the output of said detector, including means for comparingthe reference signal and the signal at the output of said detector toproduce a differential signal, and means for determining the variationof said dilferential signal.

2. An apparatus as claimed in claim 1 in which the differentialcondenser associated with the said measuring circuit is a multiplecondenser comprising a plurality of differential units, each comprisinga measuring condenser and a reference condenser formed respectively oneach side of a central plate electrode; the said central plateelectrodes decreasing in surface area along one direction of theplurality of units composing the said multiple differential condenser;the outer plates respectively disposed on each side of the said centralelectrodes each having a greater surface area than that of thecorresponding central electrode, thereby forming a plurality ofmeasuring channels having dimensions adapted to receive a range ofpossible dimensions of the materials to be examined.

3. An apparatus as claimed in claim 1, in which the plate electrodes ofthe said differential condenser each comprises plate electrodes fixed inand forming part of larger plates from which the said electrodes areinsulated with a layer of low-loss insulating material, the outer plateportions acting as anti-fringing plates to prevent electrostaticfringing-field effects at the edges of the same plate electrodes.

4. An apparatus as claimed in claim 1, in which the differentialcondenser of the said measuring circuit is formed by a plurality ofmetal plates of generally rectangular shape, each fixed as a bridgeabove two longitudinal walls of a base, also of metal, an internal c0-planar portion of each plate forming a condenser plate electrodeseparated by a layer of low-loss insulating material from the remainingexternal portion, the latter portion serving as an anti-fringing platearound the periphery of the said condenser plate and being electricallyconnected to earth through the said base, the said plurality of platesbeing an odd number, the end plates and each odd-numbered plate formingthe external plates, and the even-numbered plates forming centralplate'electrodes of decreasing dimensions, at least one of theperipheral edges of each internal plate portion which forms the commonexternal plate between two successive central plate electrodes being cutwith a bevel edge in order that its outer surfaces may be in correlationwith the corresponding facing surfaces of the said central plates.

5. An apparatus for determining the irregularity, of a continuous flowof textile or like materials, the said apparatus comprising incombination: a measuring circuit including a high-frequency generatorwith a symmetrical output: a tuned amplifier; a multiple differentialcondenser associated with the said measuring circuit; said multiplecondenser comprising; a metal base member; an odd number of metal platesof generally rectangular shape, each fixed as a bridge above twolongitudinal walls of the said base; an internal portion of each plateforming a condenser electrode, separated from the remainder of aesassaid plate by a layer of low-loss insulating material; means forearthing the external portion of each said plate; each odd-numberedelectrode forming the external plate electrodes and the even-numberedplates forming the central electrodes of a plurality of geometricallysymmetrical differen'tial condenser units, the said central electrodesdecreasing in surface area along one direction of the said multiplecondenser; means for passing the flow of material to be examined betweenthe plates of one side of the said differential condenser; a screenedchassis divided into two compartments, the said tuned amplifier beinghoused in one of the said compartments and the said oscillationgenerator in the other said compartment; two lateral edges of the saiddifferential condenser base fixed on the upper part of the said screenedchassis; two threaded rods screwed into said lateral edges and passingeach into one of the said screened compartments; means for mountingrespective coupling members of said differential condenser on saidthreaded rods, thereby forming an assembly which is movable as a unitwithin the base of the said condenser, said coupling members beingadapted to connect respectively the said oscillator to the externalelectrodes of said differential condenser and the central electrodes ofsaid differential condenser to the input of said amplifier; and aninterpretation device connected to the output of said amplifier fordetermining the variations of the signal at this output.

6. Apparatus as claimed in claim 5, and further comprising: three wiresstretched longitudinally in a plane surface between insulated fixingpoints inside the said condenser base; means for connecting the outerwires to the outer plates and the central wire to the central plates ofsaid differential condenser, the said wires being connected to thecorresponding coupling members in the said screened chassis and thusforming part of the means for connecting to said differential condenserthe said oscillator and amplifier; a transverse wall provided in saidcondenser base; two threaded holes formed in said wall so as tointroduce a balancing screw for the differential condenser between thecentral wire and one of the outer wires, and a calibrating screw betweenthe central wire and the other outer wire, the introduction of the saidcalibrating screw causing a pre-determined variation of capacity, thesaid screw being normally in the disengaged position.

7. An apparatus as claimed in claim 1, in which the said tuned amplifiercomprises: a manually-operated gaincontrol device and an automaticgain-control device, acting with a predetermined time-constant; andswitching means for putting one or the other of the said devices intooperation at will, depending on whether it is desired to determine theabsolute irregularity or the relative irregularity.

. 8. An apparatus as claimed in claim 1, in which the said tunedamplifier comprises: a manually-operated gaincontrol device and anautomatic gain-control device, acting with a' predeterminedtime-constant; and switching means for putting one or the other of thesaid devices in operation at will; the said manually-operatedgain-control device including a group of three potentiometers connectedin the cathode-return circuit of the input tube of the said amplifier,namely: a first potentiometer connected as a rheostat and having itsposition-indicating member asso-' ciated with a dial graduated inpre-determined values of nominal weight or metric number for example, ofthe flow of material to be examined; a second potentiometer connected inparallel with the first potentiometer and having its slider coupled tothe return connection of the control-grid of the said input tube, thesaid slider being set during the calibration of the apparatus; and athird potentiometer connected as a rheostat in series with the saidfirst and second potentiometers, and also intended to be set during thecalibration of the apparatus. I

9. An apparatus for determining the irregularity of a continuous flow oftextile or like materials, the said apparatus comprising in combination:a differential cori denser comprising a central plate electrode, anexternal plate electrode symmetrically disposed on each side of saidcentral electrode to form a measuring condenser and a corresponding andgeometrically symmetrical reference condenser, means for passing saidcontinuous flow between the central plate electrode and the externalplate electrode forming said measuring condenser; a high frequencyoscillation generator with a symmetrical output circuit: a measuringcircuit to determine the difference between the capacities of the saidmeasuring and reference condensers, comprising said generator, saiddifferential condenser, means for connecting said external plateelectrode to said output circuit of said generator, an output terminaland means for connecting said central plate electrode to said outputterminal; a tuned amplifier connected to said output terminal of saidmeasuring circuit and comprising a manually operated gain-control deviceand an automatic gain-control device acting with a predeterminedtime-constant; switching means for selecting one or the other of saiddevices at will: a detector .coupled to the output of said amplifier; asource of reference potential; means for comparing the signals from saiddetector and the said source; and an interpretation device fed by thedifferential signal resulting from the comparison of the signal fromsaid detector with the said reference potential.

10. An apparatus as claimed in claim 9, in which the said automaticgain-control device includes a reaction circuit formed by a low-passfilter; a further detector connected to the output of the said amplifierin parallel with the detector supplying the interpretation device; and afurther source of continuous reference potential connected in serieswith the said further detector, to the input of the said reactioncircuit.

11. An apparatus as claimed in claim 9, in which, in the automaticgain-control position, the said tuned amplifier comprising an input tubewith a grid and a cathode, and the said automatic gain control deviceincluding a reaction circuit, the said switching means couples thegrid-return of the input tube to the output of the reaction circuit, andthe cathode of the said tube over a fixed cathode-return resistance, theoutput of the reaction circuit being further connected through a diodeto a source of positive potential, in order to fix an upper limit forthe potential applied to the control-grid of the said input tube.

12. An apparatus as claimed in claim 9, in which the saidautomatic-gain-control device comprises a reaction circuit formed by alow-pass filter, a further detector connected to the output of the saidamplifier in parallel with the detector supplying the interpretationdevice, and a source of continuous reference potential connected inseries with the said further detector to the input of the said reactioncircuit, the said'low-pass filter being of the resistance-capacity typewith two sections, a damping resistance being provided in series withthe capacity branch of at least one of the said sections.

13. An apparatus as claimed in claim 12, in which the said switchingmeans is constituted by a multiple switch having a third intermediateposition between the manual and automatic control positions, in whichthird position the resistances of the said filter are short-circuited soas to enable an almost instantaneous charge of the condensers of thefilter to be effected during the transition from manual to automaticcontrol.

14. An apparatus for determining the irregularity of a continuous flowof textile or like material, the said apparatus comprising incombination: a differential condenser comprising: at least one centralplate electrode; at least one plate electrode symmetrically disposed oneach side of each said central electrode, so as to form at least onemeasuring condenser and at least one reference condenser; means forapplying high frequency potentials of a given frequency, equalamplitudes and opposite.

phases to the outer plates of each said differential condenser; a tunedamplifier; means for applying the potential of the said central platesto the input of the said amplifier; a detector coupled to the output ofthe said amplifier; an interpretation device comprising a source ofcontinuous reference potential and an aperiodic differential amplifierwith two input terminals connected one to the output of the said sourceof reference potential and the other to the output of the said detector,indicator means connected to the output of said differential amplifier,and further comprising a low-pass filter which is capable of beingshort-circuited and is disposed in front of the input of the saiddifferential amplifier.

15. An apparatus as claimed in claim 14, in which the output of the saiddifferential amplifier is coupled to an indicating instrument graduateddirectly in percentages and with a centre zero, in order to determineboth the magnitude and the sign of the diflferential signal, thecalibration of the said instrument bing effected for its extremedeflections, on the one hand by annulling the output voltage of thedetector and, on the other hand, by the insertion of a calibration screwinto the measuring condenser.

16. An apparatus as claimed in claim 14, in which said indicator meansinclude a rectifier-integrator comprising a full-wave rectifier-bridgeand an integration circuit comprising an integrating condenser and ahigh load resistance, the input of said rectifier bridge being connectedto the output of said differential amplifier, said integration circuitbeing connected across the output of said rectifier bridge, theapparatus also comprising means for temporarily disconnecting saidintegrating condenser from said integration circuit and connecting it tothe first said input of said difierential amplifier.

17. An apparatus as claimed in claim 16, in which the said integrationcircuit is shunted by a discharge circuit comprising an auxiliary sourceof direct current potential having a polarity such that it tends todischarge the integrating condenser, and a resistance of the order ofonetenth of the said load resistance, with the further provision of apush-button enabling the load resistance to be temporarilyshort-circuited.

18. An apparatus as claimed in claim 14, in which the output of the saiddifferential amplifier is connected to an indicator instrument with acentre zero, and further comprising a switch for changing-over theoutput of the said amplifier to the terminals of an integratingcondenser, and simultaneously to substitute an indicating instrumentwith a left-hand zero for the said centre-zero instrument.

19. An apparatus for determining the irregularity of a continuous flowof textile or like material, the said apparatus comprising incombination: a differential condenser comprising: at least one centralplate electrode; at least one plate electrode symmetrically disposed oneach side of each said central electrode, so as to form at least onemeasuring condenser and at least one reference condenser; means forapplying high frequency po tentials of given frequency, equal amplitudesand op posite phases to the outer plates of said differential condenser;a tuned amplifier; means for applying the po tential of the said centralplates to the input of the said amplifier; a detector coupled to theoutput of the said amplifier; an interpretation device comprising asource of continuous reference potential and an aperiodic differentialamplifier with two input terminals connected one to the output of thesaid source of reference potential and the other'to the output of thesaid detector, and further comprising a low-pass filter which is capableof being short-eircuited and is disposed before the input of the saiddifferential amplifier, the output of the said differ ential amplifierbeing coupled to the input of a device adapted to indicate the passingof the differential signal beyond two pro-determined threshold values,respectively positive and negative, the said device comprising a lowpassfilter with an adjustable cut-off frequency, and two- 16. operatingcircuits with adjustable thresholds and adapted respectively to controltwo indicator relays.

20. An apparatus as claimed in claim 19, in which each said operatingcircuit comprises a thyratron, the amplified and filtered differentialsignal being applied to the grids of the two said thyratrons through apolarising circuit comprising an auxiliary source of continuouspotential and, in parallel with the said source, on the one hand apotentiometer receiving the signal on its slider and enabling an equalpolarising potential to be applied to the two grids, and on the otherhand a branch comprising two potentiometers in series, having theirsliders respectively connected to the two grids and enabling twoindependently-variable polarising potentials to be applied to the saidthyratrons.

21. An apparatus as claimed in claim 19, in which each said relay isadapted to operate the supply contacts of an indicator lamp, one of thesaid relays causing its associated lamp to light-up in its workingposition, while the other relay lights-up its associated lamp in itsposition of rest.

22. An apparatus as claimed in claim 19, in which each of the saidrelays vis adapted to actuate a counter device.

23. An apparatus as claimed in claim 20 in which the operation of thetwo said thyratrons, the anodes of which are supplied with alternatingcurrent is rendered stable by applying the control potential to theirgrids through the intermediary of a resistance-capacity combinationhaving a time-constant of the order of the period of the saidalternating current supply.

24. In a high frequency measuring device for determining the substancecross section variations of materials such as ribbons, wicks andthreads, a measuring condenser comprising a plurality of differentialunits, each comprising a measuring condenser and a reference condenserformed respectively on each side of a central plate electrode; the saidcentral plate electrodes decreasing in surface area along one directionof the plurality of units composing the said measuring condenser, theouter plates respectively disposed on each side of the said centralelectrodes each having a greater surface area than that of thecorresponding central electrode; means for connecting all the plates ofthe reference condenser in parallel; means for connecting all the platesof the measuring condensers in parallel, thereby forming a plurality ofmeasuring channels having dimensions adapted to re ceive a range ofpossible dimensions of the materials to be examined.

25. The invention claimed in claim 24 in which the plate electrodes ofthe said differential condensers each comprise plate electrodes fixed inand forming part of larger plates from which the said electrodes areinsulated with a layer of low-loss insulating material, the outer plateportions acting as anti-fringing plates to prevent electrostaticfringing-field effects at the edges of the said plate electrodes.

26. The invention claimed in claim 24 in which the said measuringcondenser is formed by a plurality of metal plates of generallyrectangular shape, each fixed at a bridge above two longitudinal wallsof a base, also of metal, an internal co-planar portion of each plateforming a condenser plate electrode separated by a layer of low-lossinsulating material from the remaining external portion, the latterportion serving as an anti-fringing plate around the periphery of thesaid condenser plate and being electrically connected to earth throughthe said base, the said plurality of plates being an odd number, the endplates and each odd-numbered plate forming the external plates, and theeven-numbered plates forming central plate electrodes of decreasingdimensions, at least one of the peripheral edges of each internal plateportion which forms the common external plate between two successivecentral plate electrodes being cut with a bevel edge in, order that itsouter surfaces may be in cor- 17 relation with the corresponding facingsurfaces of the 1,996,063 said central plates. 2,817,815

in the file of this patent UNXTED $TATES PATENTS 5 122579 Re. 23,368Grob et a1. May 22, 1951 262,827

18 Corkran Apr. 2, 1935 Evans Dec. 24, 1957 FOREEGN PATENTS Sweden Aug.31, 1948 Switzerland Oct. 17, 1949

